The present invention relates to a user interface for specifying rules for use in mapping data between a first data model and a second data model and, more particularly, between a relational model and an object model.
Object-relational mapping tools facilitate development of application programs that utilize a relational database. A relational database stores data in tables having rows (records) and columns (fields). The tables are usually interrelated, and thus, there is a logical structure imposed on the database. This logical structure is known as a schema. Each table has a primary key, comprising one or more columns that uniquely identify a row. For example, in a table with rows of customers, a column storing each customer""s social security number may be used as the primary key because it uniquely identifies each customer in the table. A table may also have another key, known as a foreign key, associating a row in one table to one or more rows in another table. For example, where one table contains customer information and another table contains order information for the customers, a foreign key may exist to relate one customer (or row) in the customer table with one or more orders (or rows) in the order table.
Object-relational mapping tools read a database and automatically generate source code from the database. This source code contains a number of classes whose interrelationships reflect the logical structure, or schema, of the database. A class, such as a Java(trademark) class, is a data structure containing both data members that store data and function members (or methods) that act upon the data. The source code contains one class for each table in the database, and each class has a data member for each column in the corresponding table. Additionally, the classes contain function members that are used to both get and set the values for the data members and, eventually, update the database.
By using an object-relational mapping tool, a programmer can automatically generate source code to facilitate their database application development. After the source code is generated, the programmer writes code to interact with the classes in the source code and not the database, thus hiding the complexities of interacting with the database from the programmer. This allows a programmer who is familiar with object-oriented programming to code against familiar classes and not unfamiliar, sometimes cumbersome to use, database query languages.
Although beneficial to programmers, conventional object-relational mapping tools suffer from a limitation. When a programmer runs the object-relational mapping tool, it generates a default mapping including source code with classes that reflect the structure of the database at that time. However, the programmer often cannot xe2x80x9cfine tunexe2x80x9d the mapping before the conventional mapping tool performs the conversion, but rather must manually enter changes, such as performing customizations on generated classes, after mapping is complete. It is therefore desirable to improve object-relational mapping tools.